ENCAPSULATION OF TRANSITION METALS INTO CARBON NANOCLUSTERS

摘要

Fourteen transition metals were co-deposited with carbon in the conventional arc discharge. A composite anode that contained the transition metal or its oxide stuffed into central bores of the graphite rods was used. Both soot sample at the reactor walls and slag at the cathode were characterized using scanning and transmission electron microscopy, and x-ray diffraction. Encapsulation occurs mainly in the slag samples. The arc discharge was modified by having metal in molten form in graphite crucible anode and a helium jet stream flowing perpendicular to the electrodes. The process produces mostly spherical particles. The criteria determining the encapsulation tendency are discussed. A modified arc discharge combined with the decomposition of methane is used to obtain encapsulation of Cu and TiC into carbon cages. The effects of preparation parameters, including the size of the metal pool, flow rate of the gas jet, static pressure, and annealing on the particle morphology and their size distribution were investigated. Ferromagnetism and its dependence on the particle size of Fe, Co, and Ni nanoclusters were identified both in the macroscopic and the microscopic scales.